Apparatus for and method of treating and handling paper pulp and similar fibrous materials



Oct. 29, 1935.

S. D. WELLS APPARATUS FOR AND METHOD OF TREATING AND HANDLING M PAPER PULP AND SIMILAR FIBROUS MATERIALS Filed Jan. 9, 1933 5 Sheets-Sheet l ATTORNEY? Oct. 29, 1935. s D WELLS 2,018,938

APPARATUS FOR AND METHOD OF TREATING AND HANDLING PAPER PULP AND SIMILAR FIBROUS MATERIALS Filed Jan. 9, 1935 5 Sheets-Sheet 2 (f ses* INVENTOR.

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Oct. 29, 1935. s. D. WELLS 2,018,938

ND METHOD OF TREATING AND HANDLING AND SIMILAR FIBROUS MATERIALS Filed Jan. 9. 1955 APPARATUS FORy A PAPER PULP 5 Sheets-Sheet 3 h INVENTOR.

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bon particles from the ilber, the

d the ink is reduced to' a powder or Patented Oct. 29, 1935 PATENT OFFICE APPARATUS FOR AND ING AND HANDLIN METHOD 0F TREAT- G PAPER PULP AND SIMILAR FIBROUS MATERIALS Sidney D. Wells, Appleton, Wis., assignor to Lewis L. Alsted, Appleton, Wis.

Continuation of application Serial No. 619,863, June 29, 1932. This application January 9, 1933,

Serial No. 650,935

19 Claims.

This invention relates generally to an apparatus for and a method of treating or handling paper pulp or similar fibrous materials and is particularly designed and adapted for de-inking paper that has been printed upon. For example, it may be used with special advantage for the purpose of removing from paper, containing ground wood pulp, ink in which carbon black has been used as the pigment. In this connection it has been proposed to remove printing ink from paper by subjecting such paper to the action of naphtha soap and soft water and then resorting to simple filtration to separate the loosened carcarbon particles passing off with ,the filtrate. Such a method forms the subjectA matter of Patent 1,826,179, granted October 6, 1931, to Minnie E. and Bruce W. Kinyon.

This application is a continuation of and a substitute for my pending application for apparatus for and method of removing printing ink from paper, led June 29, 1932, Serial No. 619,863.

The method of the present invention diiers from the Kinyon process and other prior processes and practices in that it does not depend for its elncacy upon the use of any specific solvent or detergent but relies rather upon a novel physicalchemical action and is advantageous over such prior practices in that a more complete removal of the ink is effected and this with substantial economies in the use of the soap or solvent. ln general, the present method is more efficient and better lends itself to commercial operations on a large scale.

Broadly, the present method of removing printing ink from paper comprises disintegrating the paper and agitating it in a soapy solution until the ink is loosened from the paper and a ioamy mass, containing substantially no free liquid, is produced. Such a mass is constituted of the paper bers and innumerable soap bubbles interspersed therebetween. During the production of the mass the soapy solution emulsifles or dissolves the binder or vehicle used in the ink and the pigment of multiplicity of carbon particles. These carbon particles are taken up by the lrns of the soap bubbles. The carbon black used as a pigment in printers ink is readily wet by the soap solution and has a greater affinity for the soap films of the foamy mass than it has for the pulp fibers. After once being removed in this manner from the pulp fibers there is no longer any tendency for the carbon to at. tach itself to them again.

The next essential step in the process is the separation of the bubbles with the pigment particles thereon from the bers and this is accomplished by subjecting the mass to the action of a de-watering or de-liquoring device of vthe type known in the art as a screw press. In the screw press the mass is squeezed or pressed and the soap bubbles with the carbon particles thereon are expressed or extruded through the screen of the press leaving clean white fibers behind. The

presence of the soap bubbles precludes the bers from felting or matting together and thus forming a filtering medium, and the bubbles, on account of their elasticity, are capable of changingtheir 1 shapes and following the irregular passages through the mass. The use of a screw press is especially advantageous in that it applies the positive force in just the manner required to effect separation of the foam or bubbles from the liber. Any attempt to eifect this separation by rinsing or washing will break the iilms and allow the carbon particles to redeposit on the fibers. Furthermore, the advantage of reducing the power requirements is had. When a good foam 95 condition exists the power requirements of the screw press are reduced from to 70% on account of the lubricating effect of the soap films and air bubbles. rIhis feature possesses utility apart from the broader aspects consists in the employment of foam or soap bubbles to aid in the handling of pulp. For this general purpose the feature has the same advantage of reducing the power requirements.

commercially, it the steps of the process several times at least.v Preferably, a rod mill is used to disintegrate and agitato the paper in its soapy solution in the method herein disclosed and in its ,o

is usually desirable to repeat iirst instance. The employment of a rod mill for o this purpose is especially advantageous in that it makes possible to use only four parts of Water to one part of fiber, whereas with types of apparatus heretofore proposed for similar purposes it was necessary to use at least sixteen parts of water to one part of fiber. The use of one quarter of the water means that only one quarter of the chemicals required to produce a given concentration need be used, and similarly only one quarter of the steam ordinarily required is here essential to produce a given temperature. Finally, only one quarter of the power ordinarily needed to produce a given amount of maceration or working is necessary with the rod mill. Wherethe steps of the process are repeated then the subsequent acts of producing the foamy mass may usually be more conveniently carried out in simpler and less expensive types of devices, as, 'for example, what are known as mixing conveyors. Mixing conveyors consist simply o f a tank or some sort "of a receptacle in which twin screlwanrevolving iiights or similar devices operate to intimately mix the solution or eiiluent with the pulp cake delivered thereto from the first screw press and thereby produce a foamy mass similar to that which entered the first screw press but which, of course, contains less carbon particles.

One way of advantageously carrying out the method on a commercial scale consists in utilizlng a rod mill to effect the disintegration and the initial production of the foamy mass, then expressing approximately '75% of the foamy mass from the fibers by passing the mass through a screw press, then again beating and agitating the resultant cake from the screw press in a mixing conveyor and in the environment o f more soapyl solution, again expressing a portion of the soap bubbles from theresultant foamy-mass in a screw in a screw press. During the cycle of operations,

the rod mill, screw presses and mixing conveyors are so connected up in the system that the soapy solution is gaining the ink pigment as it travels back to the first stage of the process and the iiber is losing ink pigment as it approaches the final stage oi' the process. This is effected by introducing clear water into the system at the final stage or washing stage, then carrying the water which is expressed from the fibers back to the next to the last stage. 'Ihe water so carried back contains, of course, some proportion of soap in solution. The eiiluent from the next to the last stage is then carried back to the second stage o1' the process and during its travel back is supplied with soap in sumcient quantity to incorporate in the solution the desired percentage of soap. From the second stage the eiiluent is carried back to the rod mill or the first stage. 'I'he solution or eiiluent which is expressed from the foamy mass in the first stage is carried of! to any suitable point of discharge.- y

Soap stocks are selected which foam readily and which contain relatively high amounts of oleic acids. Saponin may also be employed. As will be understood, Saponin is a glucoside derived from vegetable fibrous material and has an ability to produce foam many times as great as that of the most eiiicient soaps. economy in practicing the method may be realized by using spent cooking liquors recovered from the digestion of fibrous material as the foam producing material. In this connection, it should be understood that in the treatment oi' iibrous vegetable materials for the liberation of the ber the incrusting matter consisting of albumenoids, pentosans, glucosldes, resin, lignins and similar substances are more or less dissolved and are removed in the Washing. Many of the substances are copious foam producers, especially in the combination in which -they exist in the spentcooking liquors and these liquors in the condition in which they exist after the fiber Washing operation or after proper modcation can be However, the utmost used for purposes where foam producers are needed.

For instance, the liquors obtained from the cooking of extracted licorice root are copious foam producers without further modification. Liquors from the mild digestion o f corn stalks with caustic soda are also copious foam producers.

In the digestion of resinous woods by the sulphate process considerable quantities of resin soaps occur in the spent liquors. These soaps are largely emulsied so that by the concentration of the liquors so that their specific gravity differs substantially from the gravity of the soaps the latter may be separated by the application of centrifugal force by means of centrifuges as, for instance, the well known cream separators.

Products from the bleaching of kraft pulps which are washed out are copious foam producers. The spent liquors from sulphite cooking have also this characteristic. dium for the calcium radical the foam producing properties may be enhanced and particularly where the subsequent reaction must take place in the neutral or slightly alkaline state. Each substance has an optimum pH which can be found by trial. The materials or soaps used must have detergent properties as well as foam producing properties. Naphtha soap might be used but care must be taken that naphtha not be used in excess as when so used it tends to retard the foaming properties of the soap. 'I'he use of naphtha soap is especially desirable in hard water as with hard water calcium and magnesium soaps are formed and they tend to impair the capacity of the solution to wet the carbon particles and set up a condition where the carbon particles tend to redeposit on the fibers. may, however, be overcome by using an excess of soap and especially so by using soft water.

As to the amount of soap, from 7% to 10% of the weight of the paper stock added to the eilluent from the third press will give good results. About 5% of the weight of the paper stock oi.' bentonite added to the water supplied to the fourth-press will further improve results and prevent coagulation of the soap that remains in the pulp when it is necessary to use hard water in the paper making operation that follows.

' Room temperature or approximately 65 F.1s satisfactory for carrying on the reaction although heating to 130 F. may slightly improve the results. The invention also contemplates the use of alkalis such as caustic soda in dilute solution to loosen the ink from the paper and in combination therewith a foam producing substance such as some synthetic soaps commercially available which are capable of exerting foam producing properties throughout a wide range of acidity or alkalinity.

'I'he accompanying drawings illustrate one type of apparatus which may be used to carry out the process and in the drawings:

Figure 1 is a diagrammatic view illustrating one By the substitution of so- 'I'his adverse tendency way of connecting up the instrumentalities uti- `press I9 into the'rod mill.

`may be employed. o

Referring to the drawings, it will be seen that the apparatus utilized for carrying out the method includes a rod mill designated generally at I.

The rod mill is of conventional construction and has the usual rotating cylinder 2 containing the rods 3. The paper is fed in through the inlet I of the cylinder and discharged from the outlet 5.

The rod mill is supplied with a soapy solution by means of a pipe 20 which connects with the screw press I9 used in the second stage of the process and carries the eilluent from this screw The action of 'the falling rods in the rod mill upon the old newspaper or other paper stock and the soap solution results in the formation of a foamy mass so that the comminuted or fibrous material which emerges from the discharge end of the mill contains innumerable minute bubbles. During the treatment in the rod mill, the soapy solution emulsifies or dissolves the binder or vehicle used in the ink and the pigment is reduced to a powder or a multiplicity of particles which is taken up by the films of bubbles as above described.

The discharge from the rod mill is carried by conveyors or by any suitable means to a screw press designated generally at 1. In the diagram for the purpose of simplicity in illustration the means for carrying the discharge from the rod mill to the screw press is shown diagrammatically as a pipe 6.

The screw press 'I is also of conventional construction and comprises an outer casing 8, a cylindrical screen 9 in spaced relation to theinner wall of the outer cylinder, and a screw I0. The depth and pitch of the thread of a screw varies from the inlet to the outlet and so that as the foamy mass from the rod mill is fed through the screw press a certain percentage of bubbles will be forced out through the screen 9 and pass on to the point of discharge through the pipe II. The rod mill and screw press constitute the first stage of the particular process being exemplified and in these two instrumentalities the essentials of the fundamental process are carried out, that is to say, the paper is disintegrated and agitated ina soapy solution to produce a foamy mass containing substantially no free liquid in which there are innumerable bubbles carrying the ink pigment and thereafter the bubbles with the pigment are expressed from the fibers.

As pointed out, however, it is usually desirable in actual practice to repeat this fundamental process, that is, to refoam the cake which is extruded from the screw press of the first stage and again express soap bubbles containing pigment particles from the fibers.

In carrying out this repetition, the cake from the first screw press 1 which consists of fibers with a certain amount of soap bubbles are carried through a pipe I2 or by any other suitable conveying means into a mixing conveyor I3. The mixing conveyor may consist of a suitable tank in which twin screws, revolving flights or similar devices, illustrated diagrammatically at I4, operate and function to intimately mix the cake delivered thereto with the soapy solution or eiiiuent delivered thereto. Because the cake is wet the action does not have to be as vigorous as that given by the rod mill where the waste paper first enters the system. It will be noted as the description proceeds that a counter-flow principle of circulating the solution through the system is resorted to in order that the solution o r eiiiuent may gain inkas it travels back through the4 first stage of the treatment and that the pulp or fibers may lose ink as they approach the final stage of the process. In other words, the dirtiest solution is working on the dirtiest paper and the cleanest solution on the cleanest paper. In fact, this is carried out to such extent that clear water washes the fibers in the final stage. In carrying out this purpose, the solution supplied to the mixing conveyor I3 of the second-stage is the effluent from the screw press I5 of the third stage reinforced with a proper amount of fresh soap stock or soap solution. As shown in Figure l, a pipe I 6 leads fromy the discharge of the screw press I5 of the thirdstage and discharges into a soap supply means IB'. After picking up the proper amount of fresh soap stock the eilluent passes on through a pipe I`I to the mixing conveyor I3 of the second stage. l

After the process has been carried to such an extent as to produce in the mixing conveyor I3 a foamy mass devoid of free liquid it is carried by any suitable means, as by pipe I3', to a second screw press designated at I9 in which it is pressed and further relieved of the solution and impurities. Leaving the screw press I9, the cake of fibers with some soap bubbles therein is carried into a mixing conveyor 2| where it is' again beaten into a foamy mass. 'I'he soapy solution is supplied to the mixing conveyor 2I through a pipe 22 which leads from the screw press 23 of the final or washing stage. Leaving the mixing conveyor 2l the foamy mass is carried through the screw press I5 wherein it is again subjected to pressure to cause the soap bubbles to pass through the meshes of its screen leaving substantially clear white fibers and some soap bubbles behind.

In the final stage which includes the mixing conveyor 25 and the screw press 23, the cake is agitated in and is washed by clear water which is supplied to the mixing conveyor 25 from a pipe 26. After the washing has been carried out to a point suilicient todissolve out the soapy bubbles the resulting mass is transferred to the screw press 23 and in the screw press the soap solution is separated from the fibers and is carried back to the mixing conveyor 2| of the third stage as just described. h

'I'he soap bubbles in the cake delivered from the screw press 23 are devoid or practically devoid of any carbon particles. Infact, it is estimated that there is not more than parts of the ink originally on the paper in the Consequently 80% of the impurities carried by` the liquor or foam on entering the press are removed by each pressing.

Usually the best results are obtained when there is substantially no free liquid in the foamy mass but the presence of a certain amount of free liquid does not defeat the purposes of the process. The expression "substantially no free liquid, as usedin the specification and claims, is intended to mean that condition in the foamy mass where there is more of the liquid taken up by the bers and the bubble illms than is free and wherein the bubble 4films are present in sufllcient numbers to take up the free particles of the ink pigment. There should not be suillcient free liquid in the mass to break down the bubbles or interfere with their capacity of taking up the particles of the pigment. y

It is to be understood that the invention is not limited to the particular number of treatments or stages described. The particular system described has been selected merely for the purpose of illustration. Any desirable number of treatments may be resorted to provided the paper is disintegrated' andworked up into a foamy mass in a soap solution so that'the particles of pigment are deposited on the surfaces of the bubbles and not on the fibers and may be readily separated from the fibers. In addition to this broad novelty, there are, however, additional advantages in the particular system shown and particularly in the counter-flow principle of circulating the cleansing solution.

Furthermore, while the invention has been described as particularly designed and adapted for use in removing carbon ink pigment from paper stock containing ground wood it is to be understood that the apparatus and-method are lnot restricted to this particular application or use, the present invention being capable of advantageous use for effecting separation from flbrous materials of various other substances or pigments insoluble in water providing that there is a sufllcient differential between the degree of attraction of the lm surfaces of the bubbles for such substances or pigments and for the fibrous material. The invention has been advantageously employed in recovering clean, fresh pulp of high quality from bleached pulp made from corn stalks but which had been badly damaged by mildew. In such damaged pulp the fruiting bodies, mycelia and spores of the fungi or bacteria had produced black and brown particles of such character and occurrence as to render the pulp unfit for use. By taking such damaged pulp and disintegrating it and agitating it in a solution having detergent and foam producing qualities until a foamy mass containing substantially no free liquid was produced and then by expressing the foam or bubbles from the bers the objectionable particles were separated from the fibers and a clean, fresh, white pulp of high quality resulted. In this instance just as when the invention was employed to separate the carbon pigment from the pulp containing ground wood, the bubbles or the film surfaces thereof attracted and held the objectionable, non-fibrous particles and when the mass was passed through the screw press the bubbles with the objectionable particles thereon were forced out through the screen leaving the fibers behind. When treating such material the steps of the process are usually repeated and the process is completed by the final Washing. l

The invention claimed is:

1. The hereindescribed process of removing printing ink from paper comprising disintegrating the paper and agitating itin a soapy solution until the inkis loosened from the paper and a. foamy mass is produced containing substantially no free. liquid and having the particles of the ink pigment carried by the films of the'bubbles of the aciaoss .ing the paper in a soapy solution until a foamy g mass is produced in which the particles of the ink pigment are carried by the film of the bubbles Y of the foam and expressing the bubbles with the pigmentparticles thereon from the fibers.

3. In the art of removing printing ink from paper, the step which consists in disintegrating the paper in a soapy solution until the solution and paper are worked up into a single foamy masssubstantially homogeneous throughout and in which the particles of the ink pigment are at- 15 tracted to and carried by the films of the bubbles of the foam. l

4. 'Ihe hereindescribed process of removing printing ink from paper comprising disintegrating l the paper while subjecting it to treatment with 20 a soapy solution until a foamy mass is produced containing substantially no free liquid and consisting of fibers and innumerable soap bubbles, on the films of which the particles of the ink pigment are held, and expressing the bubbles with the pigment particles thereon from the fibers.

5. The hereindescribed process of removing printing ink from paper which consists in disintegrating the paper in a soapy solution until a foamy ncass is produced in which the particles of 30 the ink are carried by the films of the bubbles of the foam, expressing a portion ofthe bubbles together with the pigment particles thereon from the mass, and refoaming the mass in a soapy solution and expressing portions of the bubbles together with their pigment particles until the mass is substantially free of ink pigment and finally washing the mass.

6. The hereindescribed process as set out in claim 5 and further characterized by the utilizan tion of a solution resulting from the washing step for the refoaming step preceding the washing step, and the utilization of the solution which is expressed from the refoamed mass resulting from such refoaming step as the refoaming and foam- 5 ing solutions for the preceding refoaming and foaming steps.

7. The hereindescribed lprocess as set out in claim 5 and further characterized by the utilization of a solution resulting from the washing step 5b for the refoaming step preceding the washing step, and the utilization of the solution which is expressed from the refoamed mass resulting from such refoaming step as the refoaming and foaming solutions for the preceding refoaming 5g and foaming steps and in reinforcing one of said refoaming solutions with a fresh supply of soap.

8. In the art of removing printing ink from paper, the step which consists in disintegrating and agitating the paper in a solution having 50 detergent and foam producing qualities until the 4solution and paper are worked .up into a single foamy mass substantially homogeneous throughout and in which the particles of the ink pigment are carried by the films of the bubbles of the g5 foam.

9. The hereindescribed process of removing printing ink from paper comprising disintegrating the paper in a solution having detergent and foam producing properties until a foamy mass 70 containing substantially no free liquid is produced in which the particles of the ink pigment arey carried by the films of the bubbles of the foam and separating the bubbles together with the particles of the ink pigment froml the fibers. u

10. The hereindescribed process of removing printing ink from paper comprising disintegrating the paper in a solution having detergent and foam producing properties until a foamy mass is produced in which the particles oi.' the ink pigment are carried by the films of the bubbles of the foam and in expressing fromthe mass the bubbles together with the pigment particles carried thereby. I

11. The hereindescribed process of removing printing ink from paper which consists in disintegrating the paper in a solution having detergent and foam producing properties until a foamy mass is produced in which the particles of the ink pigment are carried by the films of the bubbles of the foam, expressing a portion of theA bubbles together with the pigment particles thereon from the iibers, refoaming the fibers together with the remaining bubbles in a similar solution, again expressing bubbles together with 'their pigment particles from the refoamed mass,

,repeating the refoaming and separating steps until the mass is substantially free of ink pigment particles, and finally washing the bubbles -from the fibers.

l2. An apparatus for removing printing ink from paper comprising means for disintegrating the paper and agitating the same in a soapy solution until a foamy mass is produced consisting of fibers and innumerable soap bubbles on the films of which particles of the ink pigment are carried, means for expressing a portiony of said soap bubbles together with the pigment particles thereon from the fibers, means for refoaming the bers with their remaining soap bubbles, means for separating soap bubbles with pigment particles thereon from the refoamed mass. means for washing the soap bubbles from the fibers following the action of said separating means, and a circulating system for the soapy solution interconnecting said means to cause the soapy solution to travel through the apparatus in a direction counter to that in which the fibers are going whereby to cause the solution to gain and the fibers to lose ink as they pass through the apparatus.

13. An apparatus for removing printing ink from paper comprising a rod mill into which the paper to be treated is fed, means for supplying a solution possessing detergent and foam producing properties into the rod mill whereby the falling rods will disintegrate the paper in the solution and produce a foamy mass containing substantially no free liquid in which the particles of the ink pigment are carried by the films of the bubbles of the foam and means acting on the foamy mass produced by the rod 'mill to separate the bubbles together with the pigment particles carried thereby from the fibers.

14. An apparatus for removing printing ink from paper comprising a rod mill into which the paper to be treated is fed, means for supplying a solution possessing detergent and i'oam producing properties into the rod mill whereby the falling rods will disintegrate the paper in the solution and produce a foamy mass in which the particlottheinkpigmentarecan'iedbythelms of the bubbles of the foam, and a screw press acting on the foamy mass produced by the rod mill to separate the bubbles together with the pigment particles carried thereby from the fibers.

15. An apparatus for removing printing ink 5 from paper comprising a rod mill into which the paper to be treated is fed, means for supplying a solution possessing detergent and foam producing properties into the rod mill whereby the falling rods will disintegrate the paper in the solution and produce a foamy mass in which the particles of the ink pigment are carried by the films of the bubbles of the foam, a screw press acting on the foamy mass produced by the rod mill to separate the bubbles together with the pigment particles carried thereby from the bers, means for refoaming the fibers separated from the bubbles by the screw press and for separating the fibers of the refoamed mass from the bubbles thereof, and means for washing the fibers separated from the refoamed mass to remove any remaining bubbles.

16. In the art of removing printing ink from paper, the step which consists in disintegrating and agitating the paper in a solution having detergent andfoam producing qualities until the ink is loosened from the paper and a foamy mass is produced containing substantially no free liquid and consisting of fibers and innumerable bubbles, the particles of the ink pigment being 3o carried by the bubbles.

1'1. The hereindescribed process of removing printing ink from paper comprising disintegrating and agitating the paper in a solution having detergent and foam producing qualities until the ink is loosened from the paper and a foamy mass is produced containing substantially no free liquid and consisting of fibers and innumerable bubbles, the particles of the ink pigment being carried by the bubbles and subjecting the foamy o mass to pressure to express the bubbles with the ink pigment particles therefrom.

18. The herein described process of removing printing ink from paper which consists in disintegrating and agitating the paper "in a solu- 45 tion having detergent and foam producing qualities and containing the foam producing constituents at least of the spent cooking liquors re'- covered from a digestion of fibrous vegetable material until a foamy mass is produced in which the particles of ink pigment are carried by the films of the bubbles of the foam and then expressing the bubbles 'with the particles thereon from the ber.

19. In the art of treating fibrous material for the purpose of separating therefrom substances substantially insoluble in water, the steps which consist in disintegrating and agitating the material in a solution having detergent and foam producing qualities until a foamy mass is proeo duced containing no free liquid and consisting oi' fiber and innumerable lbubbles, particles of the substances to be separated being carried by the surfaces of the bubbles, and then expressing the bubbles with theparticles thereon from the bers.

SIDNEY D.- WELLS. 

